Twin, or dual, scroll turbocharger configurations may be used in turbocharged engines. A twin scroll turbocharger configuration may separate an inlet to a turbine into two separate passages connected to exhaust manifold runners. In this way, exhaust from the engine cylinders, whose exhaust gas pulses may interfere with each other, are fluidly separated.
For example, on an I4 engine with a cylinder firing order of exhaust manifold runners 1-3-4-2, exhaust manifold runners 1 and 4 may be connected to a first inlet of a twin scroll turbine and exhaust manifold runners 2 and 3 may be connected to a second inlet of said twin scroll turbine, where the second inlet is different and fluidly separated from the first inlet. In this way, separating exhaust gas pulses may result in an increase in efficiency of exhaust gas delivery to a turbine in some cases.
However, under some engine operating conditions, separating exhaust gas pulses as described above may reduce an efficiency of exhaust gas delivery to a turbine. For example, under certain engine operating conditions, e.g., high speed and high load conditions, separating exhaust gas pulses may result in an increase in backpressure and pumping work. This increase in backpressure and pumping work may be due to more restrictive, lower volume passages between the exhaust and the turbine in a dual scroll turbine, as compared to a passage that is not separated in a single scroll turbine. As such, the amount of exhaust gas in the cylinder may raise the pressure in the lower volume passages compared to the relatively larger volume, unseparated passage. The increased backpressure may also result in higher levels of hot residual gas in the cylinder, and may reduce the engine's output power.
One example approach for reducing backpressure and pumping work in a twin scroll turbocharger has been shown by Styles et al. in US 2014/0219849. Therein, systems positioning a branch communication valve between a first scroll and a second scroll in a twin (e.g., dual) scroll turbocharger system is provided. In an example, a branch communication valve may be positioned adjacent to a dividing wall separating a first scroll and a second scroll of the twin turbocharger. In an open position, the branch communication valve may increase fluid communication between the first scroll and the second scroll, and in a closed position, the branch communication valve may decrease fluid communication between the first scroll and the second scroll. In some examples, each scroll may include a corresponding wastegate and a corresponding wastegate valve to control the amount of exhaust gas which passes through turbine.
The inventors herein have recognized a potential issue with the example approach of Styles et al. For example, there may be cost, weight, and packaging penalties associated with an electrically actuated branch communication valve. Further, there may also be an additional burden on an engine control and monitoring system when two or more valves are implemented and adjusted by the aforementioned system based on engine operating conditions.
In one example, the issues described above may be addressed by a turbocharger system comprising a first scroll, a second scroll fluidly separated from the first scroll via a dividing wall, an adaptor coupled to an outlet of an exhaust manifold, an inlet of the first scroll, and an inlet of the second scroll, and a twisted valve coupled within the adaptor to rotate in response to a non-electrical actuation of a spring. In this way, the twisted valve may be actuated in response to an engine condition.
As one example, the twisted valve may be rotated to a first position in response to a decreased exhaust pressure where the twisted valve may maintain a separation of exhaust gas from first and second cylinder banks. Alternatively, the twisted valve may be rotated to a second position in response to an exhaust pressure greater than a force of the spring actuating the twisted valve in order mix exhaust gas from the first and second banks and decrease an exhaust backpressure.
It should be understood that the summary above is provided to introduce in simplified form a selection of concepts that are further described in the detailed description. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is defined uniquely by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure.